C-H stretching vibrational shift of benzene dimer: consistency of experiment and calculation.
C-H stretching vibrational shift of benzene dimer: consistency of experiment and calculation.
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DOI：
10.1002/cphc.200700415
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发表时间：
2007-10
期刊：
影响因子：
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通讯作者：
Weizhou Wang;M. Pitoňák;P. Hobza
中科院分区：
文献类型：
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作者：
Weizhou Wang;M. Pitoňák;P. Hobza
采用涵盖伦敦色散能的几种理论方法（RI-MP2，CCSD（T），RI-DFT-D，DFT/BH&H）研究了苯二聚体的三种低能结构. RI-DFT-D和CCSD（T）计算用于验证DFT/BH&H二聚体特性，因为只有在该水平才能进行非谐波计算。可以肯定的是，T形（C（2 v））结构，其中质子供体的C-H伸缩频率显示出显着的蓝移，是不稳定的，在任何理论水平。它是一种过渡结构或极小结构，即使在低温下也容易转变为平行位移结构或T形（C（s））结构。因此，不能检测到蓝移。另一方面，计算的非谐红外光谱的两个最稳定的结构，即，T形（C（s））和平行位移的，引起一个小的红（和没有蓝）的C-H伸缩振动的位移。这一发现与实验结果完全一致。
Three low-energy structures of the benzene dimer are investigated by several theoretical procedures (RI-MP2, CCSD(T), RI-DFT-D, DFT/BH&H) covering London dispersion energy. The RI-DFT-D and CCSD(T) calculations are used to verify the DFT/BH&H dimer characteristics, as only at this level can anharmonic calculations be performed. It is ascertained that the T-shaped (C(2v)) structure, in which the C-H stretching frequency of the proton donor shows a significant blue shift, is not stable at any level of theory. It is either a transition structure or a minimum which is easily transformed into a parallel-displaced structure or a T-shaped (C(s)) structure, even at low temperature. Consequently, no blue shift can be detected. On the other hand, the calculated anharmonic IR spectra of the two most stable structures of benzene dimer, namely, the T-shaped (C(s)) and the parallel-displaced ones, give rise to a small red (and no blue) shift of the C-H stretching vibration. This finding is fully consistent with the experimental results.